Wordpress will not upload

I've been getting a strange error with every website running Wordpress ever since I recompiled PHP 5.2.17 with the LSAPI present on LSWS 4.1.11. More specifically the asynchronous file upload script will not work (/wp-admin/async-upload.php) and the admin will get an

HTTP Error

error box. Specifications follow:

OS: Centos 5.8 x86_64
PHP: 5.2.17 / LSAPI
LSWS: 4.1.11

On 2-3 test customers I troubleshooted, the error occurred even with all the plugins turn off. Wordpress was at the latest version. The error occurs only sporadically but it is an issue. The error does not occur on an Apache installation.

- upload dir is /tmp which is mounted on tmpfs
- suexec is on
- server is Plesk 9.5
- mysql is 5.1.62
- the issue will occur randomly but it will occur. So if you try, say 20 or 30 uploads, one of them will eventually fail.

uploadprogress.so has been added, php.ini mem is over 200MB allocated, ditto for max body size. Sometimes it works but most of the time it doesn't (result == stall). It got broken since 4.1.x (was OK in 4.0.x).
Thanks for your help!

if it's fastcgi/php-fpm, since I'm lack of the experience, may not help you much. the reason not use lsapi php ?

Click to expand...

Because you don't have lsapi packages for Ubuntu? I did use lsapi with previous versions and went through the pain of compiling the package, but it is not practical for everyday's use with security fixes being pushed quite often. And since I am not concerned by performance issues and php-fpm is very close performance-wise, it would be nice that you support it since there's an obvious litespeed bug there and I don't feel like switching all conf to nginx/lighttpd